Ink receptive convertible films and process for their preparation

ABSTRACT

Ink receptive convertible films suitable for use in copying systems or projection slides are prepared by coating the surface of a transparent film with a fusible polymer material such as polyvinyl acetate with a pore forming agent such as ammonium carbonate. The polymer containing the pore forming agent to volatilize and render the film porous, and ink receptive. The film is then readily printed with a conventional ink after which the nonprinted portion of the opaque coating is rendered transparent through the application of heat and/or pressure, or the action of solvent vapors. The printed matter substantially retains the print quality it possessed during the ink receptive opaque stage.

United States Patent [72] Inventor HughT. Findlay Lexington, Ky.

[21 AppLNo. 750,322

[22] Filed Aug. 5, 1968 [45] Patented Sept.2l,l971

[73] Assignee International Business Machines Corporation Armonk,N.Y.

[54] INK RECEPTIVE CONVERTIBLE FILMS AND PROCESS FOR THEIR PREPARATION 2,790,727 4/1957 Hilborn 117/10 2,961,332 1/1960 Nairn 117/15 3,214,290 10/1965 Lamer 117/161 Primary Examiner-William D. Martin Assistant Examiner-William R. Trenor Attorneys-- l-lanifin and Clark and David M. Bunnell ABSTRACT: Ink receptive convertible films suitable for use 1 Claim, 6 Drawing Figs.

in copying systems or PIOJBCIIOH slides: are prepared by coat- U-S- the surface of a transparent a fusible polymer 7/10, 138-8 E, 133-8 W material such as polyvinyl acetate with a pore forming agent Intsuch as ammonium carbonate The polymer containing the 844d 5/04, 344151 5/02 pore forming agent to volatilize and render the film porous, [50] Field of Search 117/63, 47, and ink receptiva The fil is then readily primed with a 138-3 8, 264/41,48 ventional ink after which the nonprinted portion of the opaque coating is rendered transparent through the applica- [56] References (med tion of heat and/or pressure, or the action of solvent vapors. UNITED STATES PATENTS The printed matter substantially retains the print quality it 2,502,841 4/1950 Henderson 1 17/ 12 possessed during the ink receptive opaque stage.

COAT TRANSPARENT POLYMER III VOLATILE LIOUID ONTO BASE FILM HEAT TO REMOVE LIOUID BASE FILM COATED WITH TRANSPARENT POLYMER LAYER COAT POLYMER LAYER VIITH PORE FORMING AGENT IN VOLATILE SOLVENT FOR POLYMER LAYER HEAT BELOW IBOF TO REMOVE SOLVENT BASE FILM COATED WITH TRANSPARENT POLYMER LAYER CONTAINING PORE FORMING AGENT HEAT AT 200F TO VAPORIZE PORE FORMING AGENT BASE FILM COATED WITH POROUS, OPAOUE, INK RECEPTIVE POLYMER LAYER PRINT IMAGE ON OPAOIIE LAYER V HEAT TO FUSE POLYMER LAYER IMAGED TRANSPARENCY ATENTED SEPZI I9?! Q I 35] SHEET 1 OF 2 1 00M TRANSPARENT POLYMER IN voLAnLE LIQUID ONTO BASE FILM HEAT TO REMOVE LIQUID BASE FILM COATED WITH TRANSPARENT POLYMER LAYER COAT POLYMER LAYER WITH PORE FORMING AGENT IN voLAnLE SOLVENT EoR POLYMER LAYER HEAT BELoYY 180F TO REMOVE SOLVENT BASE FILM COATED WITH TRANSPARENT POLYMER LAYER CONTAINING PoRE FORMING AGENT HEAT AT 200F T0 VAPORIZE PORE FORMING AGENT BASE FILM COATED 7 WITH POROUS, oPAouE, INK RECEPTIVE POLYMER LAYER PRINT IMAGE 0N OPAQUE LAYER HEAT T0 FUSE POLYMER LAYER YMAGER TRANSPARENCY LRYERYYYR.

HUGH T. FINDLAY BY WW M ATTORNEY, A

PATENTEBSEP21|97| 3.607 357 sum 2 0F 2 FIG. 2b

FIG. 2c

FIG. 2B J3 INK RECEPTIVE CONVERTIBLE FILMS AND PROCESS FOR THEIR PREPARATION BACKGROUND OF THE INVENTION Liquid or solid typewriter ribbon inks have been formulated in the past for transfer from fabric or film ribbon carriers and adhesion to ink receptive papers. Smooth, nonabsorbent and relatively nonporous transparent film are notoriously nonreceptive to these same inks. Inability to print equally well on paper and transparent film has become accepted as a limitation of transfer media for typewriters and printing machines.

Commercial transparent coated films, translucents, and special ink ribbons are available that have application in copying systems, such as Ozalid, and in slides for wide screen viewing of printed matter. These films are specifically formulated for improving receptivity. However, the coated transparent films are not as receptive as paper and the translucents inhibit and scatter light transmission so that some of the advantage in ink receptivity is sacrificed in ultimate image quality.

BRIEF DESCRIPTION OF THE INVENTION It is now been found that a printed image on transparent film that is equivalent to that obtained on paper can be achieved by the method of this invention.

In accordance with this invention there is provided a process for rendering transparent films capable of receiving and retaining an ink image comprising coating the surface of the film with a layer of a normally transparent fusible polymer. Incorporated in the polymer layer is a pore forming agent. The film is heated to cause the pore forming agent to produce an open-pore polymer layer which is ink receptive. Transparencies having an ink image firmly affixed thereto can then be prepared by using conventional ink transfer media to print the image on the porous surface and subjecting the printed polymer layer to either heat, pressure, and/or solvent vapors which causes the polymer layer to fuse and become transparent in the nonimaged areas. The printed image substantially retains its original quality.

DESCRIPTION OF THE DRAWINGS FIG. I is a flow diagram illustrating an embodiment of the process of the invention.

FIG. 2, a, b, and c are cross-sectional views of an image transparency of the invention in various stages of preparation.

DETAILED DESCRIPTION The base film layer can be any transparent or translucent film upon which it is desired to adhere a printed image. Films include, for example, glass, polyethylene, polystyrene, cellulose, polypropylene, polyurethane, polyamide, polyethylene glycol terephthalate, polyvinyl chloride, etc.

The surface of the film is provided with a polymer coating comprising a normally transparent, fusible, polymer which is rendered opaque to translucent, open-pored and ink receptive by heating the layer in the presence of a pore forming agent.

The pore forming agent can be incorporated in the polymer layer by mixing it with the polymer before it is applied to the base layer. Alternatively it can be embedded into the polymer layer after the polymer layer has been applied to the base film by coating the polymer layer with the pore forming agent contained in a liquid which is a solvent for the polymer. A variety of relatively low melting, transparent polymers can be employed in making the porous polymer layer, for example, polyvinyl acetate, cellulose acetate butyrate, polyurethane, polyethylene and mixtures thereof.

The polymer layer is conveniently coated onto the film base by any conventional means from a dispersion or solution of the polymer in a volatile liquid such as water or organic solvents such as aliphatic and aromatic hydrocarbons and derivatives thereof, alcohols, ketones, etc. The thickness of the polymer layer is not critical but conveniently ranges between 0.5 and 2.0 mils when dry.

Suitable pore forming agents can be either solids or liquids. However, the pore forming agents must be volatilizable or fusible without producing a residue which might interfere with the ultimate transparancy of the printed film. Such agents include, for example, ammonium carbonate and bicarbonate, d-l camphor, pine oil, turpentine, etc. The pore forming materials can be mixed with the polymer coating layer before it is applied to the base film or they can be applied to the surface of the dry polymer film in the form of a dispersion or solution in a volatile liquid which is at least a partial solvent for the polymer layer. In the latter case the liquid partially solublizes the polymer so that the pore forming agent becomes im pregnated into and adhered to the polymer layer.

Conveniently solutions or dispersions of pore forming agent in a volatile liquid such as lower aliphatic hydrocarbons and their halogenated derivatives, alcohols, essters, ketones, aromatic hydrocarbons which boil below about C. 1,1,1- Trichloroethane, isopropanol,.hexane, and ethyl acetate are examples of suitable solvents for the polymer films. Concen trations of pore forming agent of about 10 percent to 20 percent weight are coated onto the surface of the film in a thickness to incorporate an amount of pore forming agent sufficient to give the desired degree of opacity or ink receptivity.

The polymer layer containing the pore forming agent is heated to cause the pore forming agent to produce an open pored, ink receptive, polymer structure, This porous structure is capable of receiving and retaining conventional marking liquids so that an ink image can be typed or printed on the opaque surface by any convenient means such as a typewriter or other printing machine.

As previously stated mixtures of polymers can be employed to form the opaque layer. In this case the polymers are chosen such that they are mutually insoluble at room temperature. One polymer is first coated onto the base film. The other polymer is then coated onto the surface of the first polymer as a pore forming dispersant in a volatile liquid which is at least a partial solvent for the first polymer. The solvent action causes particles of the second polymer to become mixed with the first polymer layer and firmly embedded therein and adhered thereto. Upon heating to volatilize and remove the liquid an open pore vesiculated system is formed. After printing the polymer mixture is heated and fused to form a transparent coating.

After the ink has been imaged on the opaque surface, the original transparency or translucency of the base film is easily restored by fusing the polymer layer by either subjecting it to heat, heat and pressure, or solvent vapors while the ink image will retain substantially its original sharpness and intensity.

The invention is further illustrated by but is not intended to be limited to the following examples wherein parts are part by weight unless otherwise indicated.

EXAMPLE I A 10 percent by weight solution of transparent polyvinyl acetate polymer in toluene was applied by a reverse roll coater to a clear film base of 2 mil thick polyethylene glycol terephthalate film. Sufficient polyvinyl acetate solution was applied to produce approximately a 1 mil dry coating when the toluene was evaporated in an air circulating oven at an air temperature of 250 F. To the dry solid polyvinyl acetate layer, there was added a 10 percent by weight dispersion of pore forming agent, ammonium carbonate, in a volatile liquid l,l,l trichloroethane. The dispersion was prepared by mixing the ammonium carbonate with the 1,1,1, trichloroethane in a steel ball mill for approximately .5 hours. The l,l,l trichloroethane penetrated the polyvinyl acetate layer and carried the particles of dispersed ammonium carbonate into the body of the polymer layer. The l,l.,l trichloroethane was removed using a minimum of heat (below 180F.) in an air circulating oven. The coating was applied in a sufiicient amount to give a dry caliper increase of approximately 1 mil after the deposition of the ammonium carbonate and removal of the 1,1 ,l trichloruethane. The ammonium carbonate was vaporized by heating at a temperature of 200 F. which resulted in the formation of an opaque, open pored surface on the polyvinyl acetate layer. The steps of the process recited above are illustrated in FIG. 1. A sample portion of the opaque ink receptive film was printed using a conventional typewriter ribbon and typewriter to produce a sharp, intense, ink image on the surface of the polyvinyl acetate layer. The imaged, opaque film structure was heated above 300F. for about 2 minutes which caused fusion of the porous structure so that it became transparent. The ink imaged portions retained substantially their original clarity, adherence, and intensity resulting in a transparency suitable for use, for example, as a master in a copying process or as a slide for projection on a screen.

FIGS. 2, a, b, c, d, and e illustrate the stages of the preparation of the ink containing transparency. FIG. 2a shows the stage where the polyethylene glycol terephthalate base 1 1 has a transparent polyvinyl acetate coating 13 thereon. FIG. 2b illustrates the stage at which time the ammonium carbonate 15 has been coated and impregnated into the polyvinyl acetate layer. FIG 20 shows the stage where the ammonium carbonate has been vaporized to produce open ink receptive pores 17 in the polyvinyl acetate layer. FIG. 2d shows the next stage where open pores 17 of layer 13 have absorbed an ink image 19 as by typing or printing. FIG. 2e illustrates the final reconverted transparent stage at which time the polyvinyl acetate layer 13 has been fused to make it transparent and which has firmly embedded in and adhered thereto the ink image 19.

EXAMPLE 2 The procedure of example 1 was repeated to coat a polymer layer comprising cellulose acetate butyrate and pore forming agent contained in ethanol onto a polyethylene film base having a thickness of 1 mil. Contained in the ethanol-cellulose acetate butyrate mixture was sufficient ammonium carbonate, pore forming agent, to produce a formulary comprising 70 parts by weight ethanol, l parts cellulose acetate butyrate, and 30 parts of ammonium carbonate. The polymer-pore forming agent mixture was coated onto the surface of the polyethylene film in a sufficient amount so that when the solvent was removed and the pore forming agent vaporized by heating at a temperature of about 180 F. in an air circulating oven for five minutes the dry caliper of the porous, opaque, cellulose acetate butyrate polymer layer was about 2.0 mils. An ink image was printed onto the open-pore polymer layer using a typewriter equipped with a conventional fabric ink ribbon and the base film-opaque polymer layer assembly rendered transparent by fusing the cellulose acetate butyrate layer by subjecting it to hot ethanol vapors at a temperature of about 78.5 C. for 5 minutes. The resulting transparency had firmly adhered thereto sharp, intense, ink images which were substantially unchanged from the opaque printed stage.

EXAMPLE 3 A 1 mil dry layer of polyvinyl acetate was coated onto a polyethylene glycol terephthalate film base layer having a thickness of 2 mils. The polyvinyl acetate was coated from percent by weight solution of polymer in toluene and dried as described in example 1. Two parts by weight of the pore forming agent d-l camphor, in one part by weight of ethyl acetate was coated onto the dry polyvinyl acetate layer to impregnate the camphor into the surface of the polyvinyl acetate layer.

The layer was heated at a temperature of I 10 F. or 3 minutes in an air circulating oven to remove the ethyl acetate and then causing the camphor to vaporize to produce an opaque, open pore, polyvinyl acetate coating. A sample of the dried film was imaged in a typewriter as in example 2 after which the printed sample was subjected to a temperature of 300 F causing the porous polyvinyl acetate layer to fuse and be reconverted to its transparent state. The ink image retained substantially its original sharpness and intensity.

EXAMPLE 4 A 1 mil dry coating of polyvinyl acetate on a 2.0 mil clear polyethylene glycol terephthalate film was prepared as described in example I. On the surface of the polyvinyl acetate layer there was coated a pore forming dispersion of low molecular weight polyethylene in a solvent mixture of isopropanol and hexane (Polyolefin Dispersion Xll a product of Eastman Kodak Company) in an amount sufficient to produce a dry increase in caliper of 0.2 mil. The wet coating was heated at for 1.5 minutes in an air circulating oven causing the polyethylene particles to become embedded in an adhered to the polyvinyl acetate layer. Excess polyethylene which was not adhered to the polyvinyl acetate layer was carried away by the circulating air. A translucent, open-pore, vesiculated structure resulted which was receptive to ink. After printing the structure was subject to heat at about 1 10 C. which caused the polyethylene-polyvinyl acetate structure to fuse and become transparent.

The foregoing has described a novel departure from accepted practice in that a coating is applied to a transparent film which renders the film opaque and ink receptive. The whiteness of the coated side provides contrast to and a porous tooth for the printed character which is applied. Subsequent to printing, the opaque coating is rendered transparent while the image portion retains its original intensity. The invention requires no special type of ink but is operable with conventional transfer media.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

lclaim:

1. A process of preparing an imaged film suitable for use in copying'systems, for projection slides, and the like, comprising the steps of:

a. coating a transparent polyethylene glycol terephthalate base film with a sufficient amount of a solution containing an ink receptive normally transparent, fusible, polyvinyl acetate polymer to produce above about 1 mil thickness of dry acetate polymer;

. applying to the coating a dispersion consisting of above about 10 percent of a pore forming agent selected from the group consisting of ammonium carbonate, d-l camphor, and polyethylene, and a solvent for said acetate polymer;

c. applying sufficient heat to dry and cause pores to form in the coating;

. imaging the coated film with an ink; and

e. heating the imaged film sufficiently to reconvert the film in nonimaged areas to its original transparency and retain substantially the same degree of image quality obtained during imaging of the film. 

